1. Field of the Invention
The present invention relates to an artificial cardiopulmonary circuit system excellent in organism compatibilities. More particularly, the present invention relates to an artificial cardiopulmonary circuit system having a blood contact part coated with a polyalkoxyalkyl (meth)acrylate material being excellent in blood compatibility.
2. Description of the Related Art
In recent years, medical instruments using polymer materials have been developed and used in a variety of quarters. Examples thereof include artificial kidneys, oxygenators, plasma separation membranes, catheters, artificial vessels, artificial joints, artificial skins and so forth. Artificial polymers when introduced into living organisms become foreign substances to the organisms and cause various biophylaxis reactions, so that events that are undesirable to the organisms occur. Accordingly, currently development of materials that do not cause biophylaxis reactions, i.e., those are excellent in organism compatibilities or blood compatibilities is demanded. It is known that materials having micro phase separated structures comprised by a hydrophilic phase and a hydrophobic phase are excellent in blood compatibilities, in particular platelet compatibilities. However, to attain this, phase separation of a specific size must be developed and the conditions that control this structure are limited within a narrow range, so that their use is limited. It is also known that the platelet compatibility can be developed by forming a hydrogel made of polyethylene glycol or the like on a surface of the material. However, the compatibility lasts only for a short period of time and it is difficult to develop a long-lasting compatibility. On the other hand, platelets considerably adhere to a surface of hydrophobic materials such as polypropylene and polyethylene terephthalate to cause activation thereof.
On the other hand, in the case of the compatibility to a complement system in the blood compatibility, it is known that the activity of complement is remarkable on cellulose and ethylene/vinyl alcohol copolymer and that the hydroxyl groups present in the polymers constitute the cause of activation. On the contrary, hydrophobic materials including polypropylene are known to have less complement activity (Jinko Zoki (Artificial Organ) 16 (2), pp 1045–1050 (1987)).
Polyalkoxyalkyl (meth)acrylate is disclosed in JP 4-152952 A as a material having platelet compatibility, anti-complement activity, easy controllability of surface and so forth in good balance and placed in practical use as a coating material.
However, this material is a noncrystalline polymer that has a glass transition temperature of 0° C. or less and is in a state of a hard candy and does not almost flow at room temperature but once temperature is increased, naturally it develops flowability. Therefore, for medical instruments coated with this material, the flow characteristics of the material become a big concern. That is, the material receives a great influence when it undergoes a production process to which heat is applied for evaporation of a coating solvent, gas sterilization and the like. Furthermore, during a transporting process, when left to stand in a car in summer seasons, the material is exposed to a high temperature environment, which possibly becomes a big problem in stabilization of the quality and performance of the material. Specifically, in a case where polyalkoxyalkyl methacrylate is adapted to an artificial cardiopulmonary circuit system including a hollow fiber membrane oxygenator, when the temperature is increased because of the above-mentioned cause, there is the possibility that the flowability of the polymer increases and the polymer penetrates into micro pores of the membrane to decrease the gas exchangeability of the membrane.